<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div {
            display: block;
           border:1px solid blue;
            margin-top: 100px;
            margin-bottom: 50px;
        }
    </style>
</head>
<body>
<div>aaa</div>
<div>aaa</div>
</body>
</html>